Perturbation of Nanoscale Structure of Polypeptide Multilayer Thin Films

Abstract

Multilayer thin films formed by sequential deposition of oppositely charged polypeptides on a charged surface are known from previous studies to comprise a mixture of types of secondary structure. Here, study of the perturbation of polypeptide film structure by deposition of poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate) (PSS) on the film surface has revealed differences in behavior attributable to physical properties of the peptides. The methods of analysis were circular dichroism spectroscopy (CD), ultraviolet spectroscopy (UVS), and quartz crystal microbalance (QCM). Films made of poly(L-lysine) (PLL) and poly(L-glutamic acid) (PLGA) with an average charge per monomer of about 1 were substantially more susceptible to perturbation of structure than films made of designed polypeptides with an average charge per monomer of about 0.5, despite preparation under identical conditions. PLL-PLGA films showed loss or gain of material and change in secondary structure content on perturbation, whether made of high molecular mass (ca. 90 kDa) or low molecular mass (ca. 14 kDa) polymers. By contrast, films made of very low molecular mass (ca. 3.5 kDa) designed polypeptides showed little change in secondary structure content. The data suggest that the penetrability of PSS or PAH into a film and therefore film density can depend substantially on the polypeptides of which it is made and the character of intermolecular interactions.

Multiple Functionalities of Polyelectrolyte Multilayer Films: New Biomedical Applications

“…Techniques such as UV spectroscopy, circular dichroism spectroscopy, and FTIR are usually employed to determine the structural properties of the films. Several parameters will affect the secondary structure of the film's constituents, including the structural properties of the polyelectrolytes used for assembly [63][64][65] as well as solvent properties. As previously mentioned, this includes ionic strength, [61,66] pH, [61,66,67] type of solvent, [68] hydration, [69] and temperature.…”

“…As previously mentioned, this includes ionic strength, [61,66] pH, [61,66,67] type of solvent, [68] hydration, [69] and temperature. [67] Boulmedais et al [63] and Haynie and co-workers [64] showed, for example, that adding a (PSS/PAH) layer on top of a [PLL/poly(L-glutamic)acid; PLL/PGA) film significantly changed the secondary structure of the film. The changes were different depending on whether PSS or PAH was deposited first.…”

“…However, polypeptide films made with low MW-designed polypeptides showed little disruption in secondary structure, meaning they were more resistant to PSS/ PAH diffusion. [64] …”

Polypeptide multilayer nanofilm artificial red blood cells

“…Such crosslinks increase the stability of a peptide multilayer film. [27][28][29][30] The present proof-of-concept work concerns encapsulation of Hb with PLL and PLGA; designed polypeptides might be more useful for encapsulation and for in vivo application.…”

Effects of geometrical confinement in membrane pores on enzyme-based layer-by-layer assemblies

“…The investigation of enzymes by CD on solid surfaces is scarce in the literature [53]. Up to now, monitoring of structural changes after the adsorption A c c e p t e d M a n u s c r i p t onto solid surfaces is done by comparison of the spectra of free and immobilized peptides and proteins [17,54,55]. The similarity of both spectra is relevant, yet the best way to evaluate the correlation between a native and an immobilized protein structure is to calculate the secondary structure fractions (of -helix and -sheet) using standard algorithms [53].…”